Method of recycling unsaturated polyester resin waste

ABSTRACT

Unsaturated polyester resin waste is glycolytically degraded to obtain industrially useful glycolic raw material. It is possible to synthesize unsaturated polyester resin by reacting this glycolic raw material with unsaturated dibasic acid and saturated dibasic acid. It is also possible to synthesize polyurethane resin by reacting the glycolic raw material with a diisocyanate compound.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of recycling unsaturatedpolyester resin waste, and more particularly, it relates to a method ofrecycling unsaturated polyester resin waste by chemically treating thesame and obtaining industrially valuable raw material.

2. Description of the Background Art

For example, most of buttons are made of unsaturated polyester resin.Such buttons are manufactured by punching out an unsaturated polyesterresin sheet and cutting out the intermediate products as obtained. Inthe manufacturing steps, however, about 50% of the raw material iswasted as chippings and shavings. The problem of waste disposal alsoarises in relation to fiber reinforced plastic products such as FRPships and bathtubs having matrices of unsaturated polyester resin. Thus,it is desirable to recycle such unsaturated polyester resin waste.

However, it is impossible to remelt and remold waste of the unsaturatedpolyester resin, which is thermosetting resin having a three-dimensionalnetwork structure, dissimilarly to that of thermoplastic resin such aspolypropylene, for example. Further, the unsaturated polyester resincannot be dissolved in a solvent.

To this end, there has been made study on a method of pulverizing fiberreinforced plastic (FRP) waste having a matrix of unsaturated polyesterresin and recycling the same as a filler (Yoshihiro Fukuda, Kagaku toKogyo (Osaka), 68 (2), 60 (1994)). However, the inventors have confirmedthat this method encounters such a problem that the strength of therecycled resin, which is reduced as the amount of the waste powder isincreased, entirely depends on the amount of new unsaturated polyesterresin.

There has been made another study on a method of degrading theaforementioned FRP under a steam atmosphere at a temperature of 500° C.for obtaining components such as phthalic acid (Yoshinari Kobayashi,Kagaku to Kogyo (Osaka), 66 (10), 452 (1992); Kazuhide Hamada, JunHosokawa and Masashi Nishiyama, Kobunshi Ronbunshu, 49 (8), 655 (1992)).However, the high temperature of 500° C. is necessary for thermallydegrading the FRP, and hence this method inevitably requires a specificequipment. Further, glass fiber contained in the FRP is deteriorated dueto the high temperature.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a methodof recycling unsaturated polyester resin waste by chemically treatingthe same and obtaining industrially valuable raw material with a simpleequipment, i.e., a method of chemically recycling unsaturated polyesterresin waste.

In order to solve the aforementioned technical problems, the inventivemethod of recycling unsaturated polyester resin waste comprises a stepof glycolytically degrading unsaturated polyester resin waste therebyobtaining glycolic raw material.

The present invention is applicable to recycling of not only waste ofthe aforementioned resin employed for manufacturing buttons, but generalunsaturated polyester resin waste. The unsaturated polyester resin towhich the present invention is applied may contain a filler of calciumcarbonate or the like, or may be composed with glass fiber or the like.

According to the present invention, the unsaturated polyester resinwaste is preferably crushed and thereafter glycolytically treated, sothat glycolytic degradation thereof is further facilitated. The wastecan be crushed with a hammer or chain type impact crusher, a shearcrusher, a cutting crusher, a roll, conveyor or screw type compressioncrusher, a stamp mill, a ball mill, a rod mill or the like. The grainsize of the waste powder obtained by such crushing is preferablyminimized, such that powder which is passed through a screen havingmeshes of 300 μm is advantageously employed, for example.

According to the present invention, glycol which is employed for theglycolysis is prepared from ethylene glycol, propylene glycol,diethylene glycol, dipropylene glycol, neopentyl glycol,1,3-butanediole, 1,6-hexanediole, bisphenol A hydride, bisphenol Apropylene oxide adduct, dibromoneopentyl glycol or the like.

In the glycolysis, a catalyst is preferably employed. This catalyst isprepared from sodium methylate, sodium ethylate, sodium hydroxide,methanesulfonic acid, or metal acetate such as zinc acetate, magnesiumacetate, calcium acetate, lithium acetate or sodium acetate, forexample. However, it is possible to carry out the glycolysis withoutemploying such a catalyst.

In the glycolysis, a temperature of about 150° to 250° is preferablysupplied. The upper limit of the temperature range of about 250° C. isselected in relation to the boiling point of the glycol as employed, sothat the glycol can maintain its liquid state. This upper limittemperature is preferably selected at a degree not substantiallyoxidizing the glycol.

When waste FRP is treated, the temperature which is supplied in theglycolysis will not deteriorate the glass fiber contained in the FRP,and hence the glass fiber can be recycled.

The glycolysis is preferably carried out under a nitrogen atmosphere, inorder to prevent oxidation of the glycol.

According to the present invention, as hereinabove described, it ispossible to obtain industrially useful glycolic raw material from theunsaturated polyester resin waste. The glycolysis for obtaining suchglycolic raw material can be carried out at a relatively low temperaturethrough a relatively simple operation, whereby the unsaturated polyesterresin waste can be recycled with a relatively simple equipment.

The glycolic raw material obtained in the aforementioned manner can beeffectively used as raw material for obtaining industrially usefulresin. For example, it is possible to synthesize unsaturated polyesterresin by reacting the glycolic raw material with dibasic acid, forexample. Further, it is also possible to synthesize polyurethane resinby reacting the glycolic raw material with a diisocyanate compound.

The dibasic acid employed for synthesizing the unsaturated polyesterresin includes unsaturated dibasic acid and saturated dibasic acid, bothof which are employed in general. Examples of the unsaturated dibasicacid are maleic anhydride, fumaric acid and itaconic acid. Examples ofthe saturated dibasic acid are phthalic anhydride, isophthalic acid,terephthalic acid, tetrahydrophthalic anhydride,methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalicanhydride, adipic acid, sebacic acid, chlorendic acid(1,4,5,6,7,7-hexachlorobicylo [2,2,1]-5-heptene-2,3-dicarboxylic acid),and tetrabromophthalic anhydride. The terephthalic acid can be preparedfrom that discharged through alkali reduction of polyester fiber.

The unsaturated polyester resin can be synthesized by an ordinary methodof setting a reaction temperature of 140° C. to 230° C., condensing thematerial for 2 to 6 hours while distilling water away under nitrogen,cooling the reactant, thereafter introducing 30 to 40% of styrenetherein, and adding 0.02 part of hydroquinone for serving as apolymerization inhibiter.

On the other hand, the diisocyanate compound which is reacted with theglycolic raw material for synthesizing polyurethane resin is preparedfrom toluene diisocyanate, diphenylmethane diisocyanate (MDI),naphthalene diisocyanate, tolidine diisocyanate, hexamethylenediisocyanate, isophorone diisocyanate, p-phenylene diisocyanate,transcyclohexane 1,4-diisocyanate, xylylene diisocyanate (XDI),hydrogeneration XDI, hydrogeneration MDI, lysine diisocyanate, ortetramethylxylene diisocyanate. The polyurethane resin can besynthesized by an ordinary method.

The unsaturated polyester resin or the polyurethane resin recycled inthe aforementioned manner can be employed as a molding material, anadhesive or a paint. Such resin is molded by an ordinary molding methodsuch as hand lay up molding, compression molding, cast molding,injection molding, reaction injection molding, transfer molding or thelike.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is now described in more concrete terms withreference to Examples.

In the following Examples, chippings of buttons consisting ofunsaturated polyester resin were crushed by a crusher MIYAKO DM-6 (byMiyako Product Co., Inc., rotational frequency: 28,000/min., capacity:150 g), and the powder materials as obtained were passed through screenshaving meshes of 300 μm for preparing samples.

EXAMPLE 1 Glycolysis with EtONa Catalyst

10 g of unsaturated polyester resin waste, 100 g of ethylene glycol, and2 g of EtONa were introduced into a 1L three-necked round bottom flaskprovided with a stirrer and a cooler, and treated at 180° C. for 5 hoursand then at 200° C. for 8 hours respectively. The reactant obtained bysuch treatment was filtered, washed with tetrahydrofuran (THF), anddried. 4.5636 g of remainder resin was filtered out, with a degradationrate of 54.4%. A THF solution was prepared from the degradation product,the molecular weight of which was measured through gel permeationchromatography (GPC) with reference to standard polystyrene, to observevalues of number-average molecular weight and (weight-average molecularweight)/(number-average molecular weight) of 138 and 1.05 respectively.

EXAMPLE 2 Glycolysis with CH₃ SO₃ H Catalyst

10 g of unsaturated polyester resin waste, 100 g of ethylene glycol, and2 g of methanesulfonic acid were introduced into a round bottom flaskwhich was similar to that employed in Example 1, and treated at 180° C.for 5 hours and then at 205° C. for 8 hours respectively. The reactantobtained by such treatment was filtered, washed with THF, and dried.6.6807 g of remainder resin was filtered out, with a degradation rate of33.2%. The degradation product was subjected to measurement of themolecular weight similarly to Example 1, to exhibit values ofnumber-average molecular weight and (weight-average molecularweight)/(number-average molecular weight) of 186 and 1.06 respectively.

EXAMPLE 3 Glycolysis with MeONa Catalyst

20 g of unsaturated polyester resin waste, 40 g of ethylene glycol, 2 gof sodium methylate, and 50 ml of dimethylformamide (DMF) wereintroduced into a round bottom flask which was similar to that employedin Example 1 and treated at 150° C. for 5 hours, the DMF was distilledaway, and thereafter the mixture was further treated at 205° C. for 8hours. The reactant obtained by such treatment was filtered, washed withTHF, and dried. 10.2216 g of remainder resin was filtered out, with adegradation rate of 48.89%.

EXAMPLE 4 Glycolysis with No Catalyst

10 g of unsaturated polyester resin waste and 100 g of ethylene glycolwere introduced into a round bottom flask which was similar to thatemployed in Example 1, and treated at 205° C. for 13 hours. The reactantobtained by such treatment was filtered, washed with THF, and dried.6.0431 g of remainder resin was filtered, with a degradation rate of39.57%.

EXAMPLE 5 Glycolysis under Relatively Low Temperature

10 g of unsaturated polyester resin waste, 20 g of ethylene glycol, 100ml of THF, and 1 g of EtONa were introduced into a round bottom flaskwhich was similar to that employed in Example 1, and treated at 70° C.for 13 hours. The reactant obtained by such treatment was filtered,washed with THF, and dried. 9.7670 g of remainder resin was filteredout, with a degradation rate of 2.3%.

EXAMPLE 6 Glycolysis with NaOH Catalyst

10 g of unsaturated polyester resin waste, 40 g of ethylene glycol, and2 g of sodium hydroxide were introduced into a round bottom flask whichwas similar to that employed in Example 1, and treated at 205° C. for 9hours. The reactant obtained by such treatment was filtered, washed withTHF, and dried. 4.2357 g of remainder resin was filtered out, with adegradation rate of 57.64%.

EXAMPLE 7 Glycolysis with NaOH Catalyst

100 g of unsaturated polyester resin waste, 120 g of ethylene glycol,and 1 g of sodium hydroxide were introduced into a round bottom flaskwhich was similar to that employed in Example 1, and treated at 205° C.for 24 hours. The reactant obtained by such treatment was filtered,washed with THF, and dried. 46.0 g of remainder resin was filtered out,with a degradation rate of 54.0%.

Further, 2 g of sodium hydroxide, 2g of sodium ethylate and 250 g ofdiethylene glycol were added to 46.0 g of the remainder resin, and themixture was introduced into a round bottom flask similarly to the above,to be treated at 245° C. for 8.5 hours. Then, the reactant as obtainedwas filtered similarly to the above, washed with THF, and dried. 0.8 gof remainder resin was filtered out, with a degradation rate of 98.3%.

EXAMPLE 8 Glycolysis of FRP Waste

100 g of FRP waste, 150 g of ethylene glycol, and 1 g of sodiumhydroxide were introduced into a round bottom flask which was similar tothat employed in Example 1, treated at 205° C. for 5 hours, and furthertreated at 245° C. for 9 hours. The reactant obtained by such treatmentwas filtered, washed with THF, and dried. 76.52 g of remainder resin wasfiltered out, with a degradation rate of 23.43%.

EXAMPLE 9 Glycolysis with Zinc Acetate Catalyst

10 g of unsaturated polyester resin waste, 40 g of ethylene glycol, and0.5 g of zinc acetate were introduced into a round bottom flask whichwas similar to that employed in Example 1, and treated at 205° C. for 7hours. The reactant obtained by such treatment was filtered, washed withTHF, and dried. 5.8665 g of remainder resin was filtered out, with adegradation rate of 41.34%.

EXAMPLE 10 Glycolysis with Propylene Glycol

10 g of unsaturated polyester resin waste, 40 g of propylene glycol, and2 g of sodium methylate were introduced into a round bottom flask whichwas similar to that employed in Example 1, and treated at 205° C. for 9hours. The reactant obtained by such treatment was filtered, washed withTHF, and dried. 7.6956 g of remainder resin was filtered out, with adegradation rate of 23.04%. Values of number-average molecular weightand (weight-average molecular weight)/(number-average molecular weight)obtained through GPC were 293 and 1.03 respectively.

EXAMPLE 11 Glycolysis with Propylene Glycol

20 g of unsaturated polyester resin waste, 40 g of propylene glycol, and2 g of sodium ethylate were introduced into a round bottom flask whichwas similar to that employed in Example 1, and treated at 205° C. for 10hours. The reactant obtained by such treatment was filtered, washed withTHF, and dried. 15.3695 g of remainder resin was filtered out, with adegradation rate of 23.15%.

EXAMPLE 12 Synthesis of Recycled Unsaturated Polyester Resin

The ethylene glycol degradation product (degradation product of 9.7784 gand ethylene glycol of 40 g; 0.644 mol) obtained in Example 3 wasneutralized with hydrochloric acid, 74.8 g (0.644 mol) of maleic acidwas added thereto, water was distilled away under nitrogen, and themixture was reacted at 210° C. for 2 hours, to obtain 92.1 g of recycledunsaturated polyester resin. Through GPC, the resin as obtainedexhibited values of number-average molecular weight and (weight-averagemolecular weight)/(number-average molecular weight) of 1,121 and 1.38respectively.

EXAMPLE 13 Synthesis of Recycled Unsaturated Polyester Resin

The propylene glycol degradation product (degradation product of 4.6305g and propylene glycol of 40 g; 0.525 mol) obtained in Example 11 wasneutralized with hydrochloric acid, and 20.6 g (0,210 mol) of maleicacid and 46.7 g (0.315 mol) of phthalic anhydride were added thereto,water was distilled away under nitrogen, and the mixture was reacted at210° C. for 4 hours, to obtain 68.9 g of recycled unsaturated polyesterresin. Through GPC, the resin as obtained exhibited values ofnumber-average molecular weight and (weight-average molecularweight)/(number-average molecular weight) of 1,508 and 2.01respectively. For the purpose of comparison, it is pointed out that"Polylite 210M" by Dainippon Ink and Chemicals, Inc. has values ofnumber-average molecular weight and (weight-average molecularweight)/(number-average molecular weight) of 1,646 and 3.26respectively.

45.9 g of styrene was added to 68.9 g of the unsaturated polyester resinobtained in the aforementioned manner, with addition of 1% each ofmethyl ethyl ketone peroxide and cobalt naphthenate with respect to thetotal weight of the unsaturated polyester resin and the styrene toobtain a resin composition, which in turn was castmolded underconditions of precuring at 25° C. for 2 hours and postcuring at 70° C.for 2 hours. The molding as obtained exhibited bending strength of 132.2MPa, while a molding of the aforementioned "Polylite 210M" exhibitedbending strength of 92.1MPa.

EXAMPLE 14 Synthesis of Recycled Unsaturated Polyester Resin

The propylene glycol degradation product (degradation product of 4.6305g and propylene glycol of 40 g; 0.525 mol) obtained in Example 11 wereneutralized with hydrochloric acid, 20.6 g (0.210 mol) of maleicanhydride and 52.3 g (0.315 mol) of terephthalic acid discharged inreduction of polyester fiber were added thereto, water was distilledaway under nitrogen, and the mixture was reacted under 210° C. for 4hours, to obtain 69.5 g of recycled unsaturated polyester resin. ThroughGPC, values of number-average molecular weight and (weight-averagemolecular weight)/(number-average molecular weight) of the resin asobtained were 1,500 and 2.00 respectively.

EXAMPLE 15 Recycling of Glass Fiber

50 g of unsaturated polyester resin "Polylite BS210M" by Dainippon Inkand Chemicals, Inc., containing 30 to 40% of styrene, was prepared withaddition of 1% each of methyl ethyl ketone peroxide and cobaltnaphthanate with respect to the weight of the "Polylite BS210M" and 15 gof the glass fiber recovered in Example 8, to obtain a composite resincomposition. This composite resin composition was cast-molded underconditions of precuring at 25° C. for 2 hours and postcuring at 70° C.for 2 hours. The molding as obtained exhibited bending strength of 140MPa. For the purpose of comparison, it is pointed out that a mixtureprepared in the aforementioned manner with no addition of the glassfiber and a commercially available FRP tank containing 30% of glassfiber exhibited bending strength values of 92.1 MPa and 134 MParespectively.

EXAMPLE 16 Synthesis of Recycled Polyurethane Resin

50 g of the ethylene glycol degradation product obtained in Example 3was neutralized with hydrochloric acid, and 0.05 g of triethylenediamineand 0.15 g of tin octenate (II) were added to and mixed with the same.25 g of toluene diisocyanate was added to and further mixed with thismixture, which in turn was reacted at 100° C. for 1 hour, to obtainpolyurethane resin.

What is claimed is:
 1. A method of recycling unsaturated polyester resinwaste, comprising the steps of:preparing unsaturated polyester resinwaste; and glycolytically degrading said unsaturated polyester resinwaste, thereby obtaining glycolic raw material.
 2. A method inaccordance with claim 1, wherein said step of preparing said unsaturatedpolyester resin waste includes a step of crushing said unsaturatedpolyester resin waste.
 3. A method in accordance with claim 2, whereinsaid step of preparing said unsaturated polyester resin waste furtherincludes a step of screening crushed said unsaturated polyester resinwaste.
 4. A method in accordance with claim 3, wherein a screen havingmeshes of not more than 300 μm is employed in said screening step.
 5. Amethod in accordance with claim 1, wherein said unsaturated polyesterresin waste includes waste of a fiber reinforced plastic productcontaining glass fiber.
 6. A method in accordance with claim 1, whereinsaid step of glycolytically degrading said unsaturated polyester resinwaste includes a step of adding glycol to said unsaturated polyesterresin waste.
 7. A method in accordance with claim 6, wherein said glycolincludes one selected from the group consisting of ethylene glycol,propylene glycol, diethylene glycol, dipropylene glycol, neopentylglycol, 1,3-butanediole, 1,6-hexanediole, bisphenol A hydride, bisphenolA propylene oxide adduct, and dibromoneopentyl glycol.
 8. A method inaccordance with claim 6, wherein said step of glycolytically degradingsaid unsaturated polyester resin waste further includes a step of addinga catalyst to said unsaturated polyester resin waste.
 9. A method inaccordance with claim 8, wherein said catalyst includes one selectedfrom the group consisting of sodium methylate, sodium ethylate, sodiumhydroxide, methanesulfonic acid, and metal acetate.
 10. A method inaccordance with claim 1, wherein a temperature of 150° C. to 250° C. issupplied in said step of glycolytically degrading said unsaturatedpolyester resin waste.
 11. A method in accordance with claim 1, furthercomprising a step of synthesizing unsaturated polyester resin byreacting said glycolic raw material with dibasic acid.
 12. A method inaccordance with claim 11, wherein said dibasic acid includes unsaturateddibasic acid selected from the group consisting of maleic anhydride,fumaric acid and itaconic acid, and saturated dibasic acid selected fromthe group consisting of phthalic anhydride, isophthalic acid,terephthalic acid, tetrahydrophthalic anhydride,methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalicanhydride, adipic acid, sebacic acid, chlorendic acid(1,4,5,6,7,7-hexachlorobicyclo [2,2,1]-5-heptene-2,3-dicarboxylic acid),and tetrabromophthalic anhydride.
 13. A method in accordance with claim1, further comprising a step of synthesizing polyurethane resin byreacting said glycolic raw material with a diisocyanate compound.
 14. Amethod in accordance with claim 13, wherein said diisocyanate compoundincludes one selected from the group consisting of toluene diisocyanate,diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, tolidinediisocyanate, hexamethylene diisocyanate, isophorone diisocyanate,p-phenylene diisocyanate, transcyclohexane 1,4-diisocyanate, xylylenediisocyanate (XDI), hydrogeneration XDI, hydrogeneration MDI, lysinediisocyanate and tetramethylxylene diisocyanate.